Mining of sulphur



Jan. 18, 1927.

R. H. STEWART MINING oF sULPHUR Original Filed March 15, 1924 over@ AT'TORNEYS v clay. Beneath the sulphur formation is .Patented Jan. 18, 1927.i

ROBERT HOLDEN .sTEwART,` or VANCOUVER, BRITISH COLUMBIA, CANADA, AssICNOR i To TEXAS' GULF sULrHUR COMPANY, TEXAS'. l

PATENT OFFICE.

0F NEW YORK, N. Y'.', A CORPORATION I 0F MINING OF SUIPHUR.

Original 'application led March 15,

This invention relates to improvements inthe mining of sulphur, and includes an improved-method for the mining of sulphur by underground fusion, as Well as an improved system orl apparatus therefor.

In the mining of sulphur by underground fusion, in accordance with the so-called Frasch process, a hole or well is drilled through the overlying strata to the bottom of the sulphur formation, which hole isa usually cased With an eight-inch or teninch pipe, and then, through a system of concentric 'pipes appropriately arranged Within this casing, superheated Water is pumped down to the foot of the hole or Well where it is dischargedy into the sulphur formationA andmelts the sulphur. `The melted and liquid sulphur enters onel of the concentric pipes, yusually through a strainer, and is raised to the lsurface of the ground, generally by 'means of an air lift.- The Well lcontinues t'o operate and produce sulphur until the sulphur-bearing formation is locally exhausted, or until the piping equip- `ment is broken by subsidence of the ground due to the extraction of the sulphur content. l The sulphur formation is usually found in 'the' form of so-called domes, at depths varying from around 500 to 1500 feet below `the surface of the ground. These sulphur domes are usually overlaid by a porous cap rock formation of limestone which in turn is overlaid by gumbo, quicksand and c drite, and layers or domes of salt.

The sulphur formation itself usually con- 'tains the sulphur distributed in a porous rock formation which also contains a large amount of Water forming what may be considered an underground lake of brine or salt Water containing, for example, about 4800 grains per gallon of solids in solution, mainly sodium chloride, and in addition hydrogen sulphide and other soluble l sulphides.

In the so-called Frasch system of mining sulphur by underground fusion, hot Water bis the vehicle commonly used for conveying and transmitting heat to the sulphur. Inasmuch as sulphur melts at a temperature i924, serial No. 699,448. Divided and 18, 1926. serial No. 95,542.

around 240 F., vvhich is above the boiling lpoint of water at atmosphericpressure, the eating Water ishighly superheated and is uns appimauon mea march l pumped into the mine under a highppressure. Y The temperature to which the water can be superheated is however limited by the dan' ger of overheatin the sulphur in which case it becomes viscous. Accordingly, the

Water is heated to a temperature which avoids overheating s of the sulphur but which is sufficiently above the melting point i of the sulphur to hringabout effective melting thereof as the highly heated Water comes in contact with the underground sulphur. The Water may thus be heated under pressure to about 320 F. and pumped into the sulphur deposit, 'this water replacing the sulphur removed by the` well together with water already contained in the deposit v which may be withdrawn by` means O bleed-wells, situated atv suitable points in the deposit. The bleed-Wells are usually' located so as to Withdraw the cold brine or salt water from the lower part ofthe sulphur formation.

The sulphur dome ymay underlie a considerable surface area of ground. The domel may, for example, be as much as a mile in diameter; and the underground lake vforming a part of the deposit or adjacent thereto may contain billions of gallons of underground water or brine. l

In the mining of such a sulphur deposit one or several Wells are usually drille and operated at one part of the deposit until the sulphur bearing formation is exhausted locally and then other Wells lare drilled at another part of the deposit, and the depositv is progressively Worked in this way until exhausted. The operation off-ja sulphur mine in this way 1s an operation of large magnitude. Water which it is necessary to pump into the deposit in a single day may amount to several million gallonsI in commercialoperations.

The pumping of a large amount of superheated Water into thedeposit results in the The amount of highly heated v gradual accumulation of a progressively increased lamount of hot Waterv in the deposit.

The specific gravity ofy the original deposit water is for 'example about 1.08, and the tem erature for exam le about 108 F.; w e the specific gravlty of the clean hot water pum ed into the mine is in the neighborhood o 0.91. Owing to this difference in specific gravity, the hot water rises 'or tends to rise to the top of the dome, displacing the cold deposit water downward, and, while there is some diffusion and mixing, in a general way the water at the top of the dome becomes cleaner and hotter with only a small amount of solids in solution, while the water in the lower part of the deposit contains its original content of dissolved solids until displaced by the cleaner water from above.

The continued supply of a large amount of highly heated water to the mine forms one o the major expenses of the operation, this water being commonly obtained from a source several miles distant from the mine at a temperature around, for example, 68 F., and being heated to a temperature around 324 F. before it is pumped into the mine. Of the total heat supplied to the water, only a small part is available for melting t e sulphur. Thus, in heating water from 68 F. to 324 F., 256 B. t. u.s are supplied by the combustion of fuel to each pound of water which is pumped into the deposit. Since sulphur melts at around 240 F., the only eiective heat lsupplied to the water is that between the maximum temperature of the water and the melting Eoint of sulphur, for example, around 85 t. u.s of the total of 256 B. t. u.s supplied to the water.

The present invention provides an improved method and system of mining sul' phur whereby important economy o f operation is obtained, and whereby a greatly increased fuel eiliciency, and decreased fuel consumption can be effected. The present mav be as high as 300 F., or even higher.

application is a continuation of my prior ap.- plication, Serial No. 699,448, filed March 15, 1924.

The present invention is of particular advantage in the mining of sulphur from deposits which have been operated for considerable time until there has accumulated a large amount of hot water in the u per portion of the dome or formation from w ich the sulphur has been exhausted. After long periods of operation, the temperature of this' hot water, accumulating in the upper por- .tion of the dome, will be considerably above the melting point of sulphur, which is about 240 F., andthe temperature of this water This hot water is contained under considerable pressure, which pressure 1s usually in excess of the hydrostatic pressure.

According to the present invention.' I

make further use of the accumulated hot waterA in' the dome and take advantage ot the heatwhich it contains so that it becomes vconsiderably in excess of 240 unnecessary to supply additional fresh hot water to the sulphur deposit for use in the further mining of sulphur, or so that only a minimum amount of additional heat need be supplied, and, where supplied, can be supplied without supplying further amounts of fresh hot water.

In the carrying out of the present invenit under pressure through the well where the.l active mining operation is going on.

Where the water withdrawn is sufficiently hot, i. e., sufficiently above the melting point of sulphur, it can be maintained at its high temperature and Areintroduced into the deposit through the active sulphur mining well with only a small loss in temperature. The hot Water so introduced in the localized well zone Will tend torise again, after serving its purpose of melting sulphur, to unite with the large body of hot water in the top of the deposit. The gradual withdrawal of hot water in this way, with return of the hot water withdrawn to the deposit, will result in a tendency to reduce the temperature of the hot water in the deposit, but after a deposit has been operated a long period of time, the underground lake of hot water will be so large that water can 'be withdrawn from it and pumped back into the operating well or wells for long periods of time without reducing the temperature of the hot water below that at which it is effective for the mining operation.

The process of the present invention can be carried out to particular advantage when the original mine water has been subst-an'- tially all withdrawn from the sulphur deposit through bleed-wells from the lower levels of the deposit and when this watery has been replaced by hot water. By then withdrawing hot water at th`e same rate at which it is introduced into the active wells, the amount of underground hot water remains substantially constant.

-In the carrying out of the process of -the invention the hot underground water, which is at a high temperature and ressure, e. g. and up to around 300 F., or more, and at a pressure greater than atmospheric. is withdrawn and kept under pressure while it is being withdrawn, by means of a pump, a steam injector or other suitable means, and this water so withdrawn under pressure and with a temperature maintained by the pressure and by preventing vaporization, is again introduced be used again without purification.

this water under pressure, and of preventing '1t from being cooled below 2400 F., through reduction of its pressure,"is to introduce aV centrifu al pump into the line through which t e water is withdrawn, and at a sufficiently low level to receive the water while still under sufficient pressure yto prevent itsI partial vaporization.

The hot water thus withdrawn may, if desired,gbe purified, but ordinarily it can So also, the water withdrawn may be subjected to further heating, as by injection of steam, but if the water is at a sufficiently high temperature it can be used again without further heating. -V

The invention will be further described in connection with the accompanying drawing, which illustrates in a conventional and graphic manner a section of a mine and of apparatus embodying the invention and adapted for the practise of the process of the invention.

The showing is largely conventional, and

various parts are magnified, and the horizontal dimensions of the pipe and of various parts are magnified for convenience of illustration.

In such a mine as represented in the accompanying drawing, the sulphur deposit is usually overlaid by a caprock formation of limestone, above which is gumbo, quicksa-nd and clay.. Below the sulphur deposit there are usually bodies of gypsum and salt.-

In the drawing, there is represented a region marked hot water zone from which it is assumed the sulphur-has been melted, and which is assumed ,to be full of hot water accumulated from the mining operation. The hot water will also extend upwardly into the porous caprock. It will be apparent that as the sulphur is melted and withdrawn, the space originally 0crupied by the sulphur mustbe. filled either.

being 'made up as usual of a series of concentric pipes within a casing tube. For convenience of illustration, the entire series of pipes is omtted and only two concentric pipes are shown, the inner pipe 3 being 1ntended to illustrate graphically the vpipe through which the molten sulphur is pumped from the mine and which extends lto the bottom of the deposit, and the outer easing 2 illustrating the outer 'pipe withinwhich the hot water is pumped down into the mine.

A bleed-well 57is shown as located at a distance from the active sulphur mine and as leading from a lower level of the depositfrom which the colder water may be withdrawn in regulated amount.

A well 6. is shown as located so as to withdraw water from the top of thedome. This well extends down into the porous caprock and at its upper end is enlarged so as to accommodate a suitable pump, shown as a centrifugal pump 8 driven by a motorl 9 and having an extension 10 extending down into the hot water zone and which may terminate in a perforated end `11 through which the hot water is admitted into the pipe 10 and thenceA into the centrifugal pump 8. The well pump 8 may be of any suitable construction for keeping the water -under pressure so that no expansion or vfreeing of steam can take place near or at the surface of the ground. A heavy duty centrifugal pump such as a Laynefj,

multi-stage centrifugal pump can be used. This pump should be located at a suliicient distance below the surface ofthe ground to receive the water before its pressure has been reduced sufficiently `to permit vaporization and cooling thereby. The pump may be located for example from 60ato 100 feet below the surface of the ground', or it may be located lat even a lower level ifl desfred.

The water pumped from the ground passes through the pipel 13 to the well 1 where it is ,again rforced down into the ground. A pump 17 yis provided which may supplement the centrifu al pump 8, but with a suitable centrifuga pump, the pump 17 may be omitted, or may be used only forsupplementing the centrifugalpump as oc casion may arise for doing so.

By withdrawing the hot water from the mine in this way and maintaining it under pressure and at its origmaltemperature, or

with only a minimum drop in temperature,

the. water can be used over again in a different location of the mine for melting further amounts 'of sulphur. This re-utili zation of the hot mine waterresults in-large economies as compared with ordinary min 'i ing operation where hot water is provided and pumped down into the mine for melting thesulphur and where theheat required for heating the fresh water, e. g. from 68 to around 324 F. is 256 B t. uis.- By avoiding the-necessity of supplying such fresh hot water, and by utilizing the accumulatedhot water from the mine, it becomes possible to avoid the large consumption of heat now involved in commercial mining operation. A

At the beginning of the mining operations of the dome, the sulphur wells are advantageously located near the top of the dome near the location of the well 6 and such wells are operated until the sulphur is exhausted at that location or until subsidence of the ground causes breaking of the piping equipment. As the ground surrounding the first wells becomes exhausted, additional wells are drilled at a distance from the first wells. These wells may be at a location such as illustrated by the well l in the drawing and the Well 6 may be an exhausted Well which is used merely for the purpose of withdrawing the hot Water from the upper part of the deposit. The upper part of the deposit forms a heat reservoir where the hottest water tends to accumulate in a portion of the deposit from which the sulphur has been exhausted and in the porous caprock where it serves no useful purpose in melting sulphur and where it causes great heat loss and low heat etlicency.

Such operations represent the usual operations and it is from such operations that the resent invention is dierentiated. lnstea of introducing additional hot water as in such prior operations, the process of the present invention is carried out with the use of the hot water accumulated in the deposit itself. If this water is withdrawn through bleeder Wells, the reduction in pressure will cause reduction in temperature by vaporization and the water escaping at the surface -Will have a 'temperature not exceeding 212 F. which is a temperature too low for further use in the melting of sulphur. According to the present invention, such reduction in temperature due to vaporization is avoided by maintaining the hot water under a suicient pressure to prevent cooling by vaporization so that it can be maintained at substantially its original temperature and reintroduced into an operating well or Wells while still under pressure and at approximately its original temperature. If, for example, the temperature of the accumulated body of hot water in the deposit is in the neighborhood of 275 to 300 F., this water is withdrawn under suit cient pressure to prevent vaporization and cooling and iskept under pressure and forced again down into the deposit at the Asure were not maintained; but by withdrawn or not materially vbelow such temperature. t

ln my prior application, Serial No. 699,- 448, l have described and claimed a process in which the Water Withdrawn from the deposit is further heated to increase its temperature by a mixture with additional amounts of super-heated water in regulated proportion. The present application is a continuation of said prior application, but the invention claimed in the present application is limited to a process in which the hot water withdrawn from the deposit is used over again by pumping it back into the deposit without any material increase in temperature, the hot water from the deposit being withdrawn at'a sufficiently high temperature and being maintained at such temperature and being reintroduced While sti-ll at a sufficiently high temperature, without additional heating to any considerable extent, so that it is made use of for further mining operations.

The present process can be considered to.

involve a re-utilization of the hot accumulated mine water by recirculating it from the exhausted portion of the deposit to a part of the deposit where mining is to be carried on. Where this recirculation is accomplished by withdrawing the superheated water from its zone of lhigh pressure, the advantages of the high temperature lwould be lost by reduction in pressure and resulting vaporization if the presmaintaining the pressure on the water withdrawn so that the Water at the surface of the ground passing through the circulating line is under a correspondingly high pressure, the superheated character of the water is maintained and this is made use of by pumping the Water down in the operating well or wells where its high temperature is made use of for melting additional sulphur.

Instead of requiring a large amount of fresh superheated water, with the large fuel consumption necessary to produce it, the t present invention practically eliminates the need 'of supplying heat except for the mechanical'operations of pumping, compressing air for the pumping of sulphur, lighting, heating, etc.

The present invention not only makes use of the accumulated hot water which is ordinarily considered to have served its usefulness, but it applies this in a localized Way at the points of the further mining operations such that there may be considered to be a cycle ofcirculation from the hot water at the top of the deposit through the outside circulating line where the water is maintained under pressure to the operating Well or Wells where the hot water serves to melt additional sulphur and thence under-- ground through the deposit from the operatof hot water in the sulphur deposit. By

circulating large amounts' of the water in this way a similar heatingeiect can be obtained as where more highly superheated water is introducedinto the deposit. Overheating locally may thus be avoided anda more uniform distribution of the hot water underground obtained because of the greater volume of water circulated and because of the decreased difference in density or speciic gravity between the water so introduced and the surrounding vwater of the deposit. v

The present invention includes as an ap paratus or system an arrangement of wells, one or more of which is connected with the hot accumulated body of water in the dome and one or more of which are used as the active operating wells, with outside connections such that the water can be withdrawn and directly reintroduced, without substantial loss of temperature, .and maintained continuously under pressure@ This system or lapparatus requires only suitable pumping means and pipe connections for withdrawing the `hot water and maintaining it under pressure and forconveying it to the operating mines and forcing it down into the deposit. i

Where the mining operation is carried out with a hot brine of high specific gravity, which tends to settle to the bottom of the sulphur deposit, this accumulated, heavy brine can, after it has reached a sufficient volume and temperature, be withdrawn and reintroduced in a similar manner to that above described in connection with the use of hot water. The operation will be somewhat reversed, however, in that the heavy brine will be introduced at a higher level than that from which it is withdrawn and the accumulated body of hot brine will be in the lower parts'of the sulphur mine or deposit rather than in the upper portion thereof.

I claim:

1. The improvement in the mining of sul hur by underground fusion from artia ly exhausted sulphur deposits, w ich comprises withdrawing from the upper part of a de osit hot "water at a temperature higher t an the melting point of sulphur, maintaining the temperature of the water above the melting point of sulphur, and reintroducing the withdrawn hot water into the de osit at a localized well zone remote from t e point of withdrawal.

2. The lmprovement in the mining of sulphur by underground fusion from partially exhausted sulphur deposits, which com rises withdrawing from the upper part of t e deposit hot water above the melting point of sulphur, which water has preferentially accumulated in the upper part of the dcposit,

maintaining the temperature of the withdrawn water above the melting point of sulphur, withdrawing cold` water at a temperature below the melting oint of sulphur, and reintroducing the with rawn hotwater into the deposit at a localized well zone remote from the point of withdrawal.'

3. The improvement in the mining of sulphur by underground fusion from partially exhausted sulphur deposits, which comprises withdrawing part of the hottest water from the exhausted upper art of a deposit, main-v taining the'water wit drawn under pressure to prevent vaporization and lowering of temperature below the melting point of sulphur, `and reintroducing the withdrawn hot water at a 'localized well zone remote from the point of withdrawal.`

Al. The improvement in. the mining of sulphur by underground fusion from partially exhausted sulphur deposits, which comprises withdrawing from the deposit hot brine at a temperature considerably above the melting point of sulphur, maintaining the withdrawn brine under pressure to -prevent vaporization and cooling below the melting point of sulphur', and reintroducing vthe withdrawn hot brine into the deposit at a well zone remote from the point of withdrawal.

5. In the mining of sulphur by underground fusion from partially exhausted sulphur deposits, one or more wells arranged to wells extending to the sulphur containing I deposit for introducing superheated water into the deposit and removing the molten sulphur therefrom, one or more wells extending to the u per part of the deposit from which the s phur has been' exhausted, pumps so located and designed to withdraw ot water at a temperature above the melting point of sulphur from the upper part of the deposit through the last mentioned wells, means for maintaining the withdrawn hot water under pressure and returning it to said first mentioned wells, and means for with-` drawing cold water at a temperature below the melting level of the eposit.

In testimon whereof I aiixm signature.

Rosalia." HOLDEN sr waar.v

oint of sulphur from a'lower 

